This invention relates to an improved device for planetary electrode wire feeding, such device having means for the automatic adjustment of a calibrated wire-advancing force. The device may be used to advantage in the field of semi-automatic and automatic electric arc welding.
There is a known planetary electrode wire feeding device with a calibrated adjustment of the wire-advancing force. Such device comprises a body, on one side of which and radially with respect to the path of feeding of the electrode wire, there are provided substantial beds with pistons disposed therein. A wire feeding roller is axially fastened to each piston, the axes of said wire feeding rollers forming an angle between them. Spaced axially from the rollers the device has an elongated cylindrical part to which there is attached a freely guiding cone, the cone being limited by a regulating nut, the cone being threadedly connected to the other end of the hollow cylindrical part of the body.
Between the guiding cone and the periphery of the body, i.e., on its hollow cylindrical part, there is disposed a calibrated spring which thrusts the guiding cone against the regulating nut. In addition, the periphery of the body has a plurality of cut-outs wherein two-armed levers are pivotally fastened. One of the ends of said two-armed levers lie upon the front part of the pistons, while the other end, by means of a roller, engages the outer surface of the guiding cone.
The electrode wire is fed forwardly with a constant force by the above-described known device. The main drawback of such prior device is the fact that it cannot be automatically adjusted, a repeated manual adjustment being required with each new electrode supply reel.
There is another known planetary wire feeding device, such device having an automatic adjustment of the wire-advancing force. Such second known device is, in fact, an improvement upon the first above-described device. In such second known device, the guiding cone has an elongated cylindrical hollow portion which is provided with an accurate thread, the cone being screwed upon a threaded cylindrical portion of the body of the device. The guiding cone is fixedly connected with the shaft of the electric motor which drives the whole device, as well as with the housing wherein the mechanism is located.
With the last above-described known device, an automatic adjustment is ensured in accordance with the diameter of the electrode wire and the advancing force applied thereto. A very substantial defect of such device, however, is that the wire-advancing force is affected by centrifugal forces during the operation of the device; a further defect of such device is that it does not work with a calibrated adjustment of the said wire-advancing force.
A disadvantage which is common to all of the above-described prior wire feeding devices is that the wire-advancing force is affected by the coefficient of friction between the wire-feeding rollers and the electrode wire itself, such coefficient substantially increasing with a decrease in the rate of feeding of the wire.